As hardware for reproducing and storing high resolution or high quality video content is being developed and supplied, a need for a video codec for effectively encoding or decoding the high resolution or high quality video content is increasing. In a conventional video codec, a video is encoded according to a limited encoding method based on coding units having a predetermined size.
Image data of a space domain is transformed into coefficients of a frequency domain via frequency transformation. In a video codec, an image is split into blocks having a predetermined size, discrete cosine transformation (DCT) is performed on each block, and frequency coefficients are encoded in block units, for rapid calculation of frequency transformation. Compared with image data of a space domain, coefficients of a frequency domain are easily compressed. In particular, since an image pixel value of a space domain is expressed according to a prediction error via inter prediction or intra prediction of a video codec, when frequency transformation is performed on the prediction error, a large amount of data may be transformed to 0. According to a video codec, an amount of data may be reduced by replacing data, which is consecutively and repeatedly generated, with small-sized data.
In particular, it may be possible to apply a method of adjusting a reconstruction sample value by an adaptively determined offset to a sample in order to minimize an error between an original image and a reconstruction image in a video encoding and decoding operation.